A Few Things Ill Considered

Efficient hydrogen production?

Posted by coby on November 19, 2007
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Hydrogen powered cars have such an immediate and naive appeal. I mean just imagine nothing but water vapour coming out of your exhaust pipe! What could possibly be wrong with that?

Well as with most deus ex machina solutions to our oil dependence, this one has some rather glaring and inconvenient difficulties, in a very similar way to biofuels.

Specifically, the problem with hydrogen powered vehicles is not with the burning of the fuel, but its production. Because there is no earthly source of ready to go hydrogen, this product is actually better thought of as energy storage, rather than an energy source. In other words, it takes a lot of energy to produce hydrogen, energy that is thus stored for later use when it is burned.

However, there is some possible good news I cam across via a Yahoo News article. In a recent paper that appears in the Proceedings of the National Academy of Sciences, the authors describe a new twist on an old method called electrohydrogenesis. Quoting from the news article (not the paper!):

The method used by engineers at Pennsylvania State University however combines electron-generating bacteria and a small electrical charge in a microbial fuel cell to produce hydrogen gas.

Microbial fuel cells work through the action of bacteria which can pass electrons to an anode. The electrons flow from the anode through a wire to the cathode producing an electric current. In the process, the bacteria consume organic matter in the biomass material.

An external jolt of electricity helps generate hydrogen gas at the cathode.

In the past, the process, which is known as electrohydrogenesis, has had poor efficiency rates and low hydrogen yields.

But the researchers at Pennsylvania State University were able to get around these problems by chemically modifying elements of the reactor.

In laboratory experiments, their reactor generated hydrogen gas at nearly 99 percent of the theoretical maximum yield using aetic acid, a common dead-end product of glucose fermentation.

“This process produces 288 percent more energy in hydrogen than the electrical energy that is added in the process,” said Bruce Logan, a professor of environmental engineering at Penn State.

I expect there are many devils in the details, but it certainly seems like an encouraging development.

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Comments

  1. #1 Charles Barton
    November 24, 2007

    The problem with hydrogen is not just production, but storage.
    Under pressure the tiny H2 molecule diffuses through the crystal structure of steel or other metals. This hydrogen leak will cause a significant fuel loss overnight. Hydrogen cannot be stored in hydrogen filling stations, or shipped by pipeline, because of leaks. The leak of hydrogen into the crystal structure of metal storage containers decreases the metal’s flexability until it becomes brittle and then the pressure of the remaining hydrogen will simply rupture the storage container. The problem is widely recognized:
    http://weblog.xanga.com/bartoncii/628769680/vw-concept-car-has-65-mile-plug-in-range.html

  2. #2 Eli Rabett
    November 24, 2007

    So where do you put the dead bacteria?? Calculate the volume you would need. TANSTAAFL

  3. #3 John Mashey
    December 3, 2007

    I’d agree that economic hydrogen-powered vehicles seem unlikely any time soon, if ever.

    I recommend as a useful source:
    Benjamin K. Sovacool, Marilyn A. Brown,
    “Energy and American Society – Thirteen Myths”, 2007.

    “Energy Myth Four – The Hydrogen Economy is a Panacea to the Nation’s Energy Problems”, by Joe Romm is a good analysis [if you search for hydrogen over in climate.progress.org, Joe has several articles on this.]

    Maybe there will be a role for reversible-cell things like Bloom Energy SOFC to use H2 as a storage mechanism for local wind/solar intermittent systems, although I haven’t seen enough yet to have a strong opinion versus the alternatives.
    ==========
    However, I don’t understand lumping hydrogen with biofuels.
    Biofuels certainly have issues, but:

    a) A lot of knowledgeable people think that hydrogen is unlikely for vehicles, but biofuels are pretty reasonable, and don’t face the nearly-impossible total simultaneous redesign of vehicles and infrastructure on top of the hydrogen difficulties of storage and distribution. [See Joe Romm's comments, page 119-122 of the above].

    - It costs ~$100 to make a car flex-fuel (FF) right now, less later.
    - Brazil has gotten a long way with FF vehicles.
    - A lot of gas in CA & elsewhere is 10% ethanol already (E10), and E85 is widely available in some states. I.e., ethanol certainly has issues with regard to pipelines, but still, ethanol gets distributed.

    b) Many think that corn ethanol is just a temporary, but useful transition stage towards cellulosic ethanol, based on switchgrass or miscanthus (elephant grass), for example. I’m an old farmboy: farmers grow whatever makes them more money, and miscanthus uses less water and fertilizer than corn. Corn was never bred as a fuel plant, but it has the advantage of substantive existing infrastructure. We’ve had millenia to breed food crops. We should be able to take things like miscanthus (already good) and make them better, and places like U of Illinois and UC Davis and others are trying. One can expect classic incremental agricultural progress, not requiring giant breakthroughs.

    c) But even corn ethanol isn’t so bad: people frequently say that it is energy-negative … but it turns out that there are a lot of studies with different assumptions, and most of them especially lately, say it’s positive. The negative view comes primarily from various papers of David Pimentel and his associates, and for some reason, those get cited heavily. Maybe he is right, but it’s worth reading “Energy Myth Three” in the book above for other views.

    d) It certainly seems that as fast as possible, we should get to:

    - Plugin-electric vehicles for short-range usage.
    [I recently saw an electric version of the Mercedes SMART car running around Palo Alto - pretty cool.]

    - Plugin-electric hybrid flex-fuel cars for general use.
    Concept examples: Chevy Volt or Toyota 1/X.

    - Of course, as much renewable-source, and preferably distributed generation, electricity as possible.

    As Joe Romm says (page 120):
    “PHEVs that are also flexible-fuel vehicles capable of operating on gasoline or biofuel blends may be the ultimate vehicle.”

    I also have some hope that with all the effort on thin-film photovoltaic, people can eventually integrate PV cost-effectively into auto surfaces to extend the battery-only range of cars, so that more commutes avoid fuel use, even without plugin stations in parking lots. [A SMART Fortwo EV is supposed to use 193 Wh/mile, with a range of 62 miles. Suppose you have:
    30 minute commute
    9 hours at work
    30 minute commute back

    and suppose you get 193Watts (a bit high, but make it easy) from PV. On a good day, that gets you another 10 miles range, or +16%. Of course, with a charging station at work, you can almost double the range, or the battery-only range of a PHEV.]

    e) For some agricultural uses, electric-only vehicles seem quite suitable, as in:

    http://www.renewables.com/Permaculture/ElectricTractor.htm

    Fortunately, unlike cars and trucks, most farm machinery stays closer to home, which helps a lot. Assuming that:
    - there are easy-to-switch battery packs [as in the above design]
    - and the batteries & motors provide adequate horsepower
    (the design above seems to overlap with the small/medium tractors of the current John Deere product range; I haven’t yet seen an electric design that matches the 200-500HP tractors or combines in http://www.deere.com ; that doesn’t say they’re impossible, but the difference in energy density between biodiesel and batteries is still awkward for the higher power requirements.)

    I’d guess that the natural evolution is for the small/medium tractors to go all-electric, and the bigger machines to stay fueled for a good while.

    f) For medium/long-distance transport [for food and anything else], I still haven’t seen a clear electric-only solution, which means there is likely a continuing ethanol/biodiesel requirement. Current North American agriculture depends strongly on huge, efficient farms that happen to be located fairly far away from their markets. [One can argue whether or not this was a good idea, but it is what it is, and it does allow 2-3% of the population to (over)feed the rest of us and still ship crops elsewhere. Of course, with Peak Oil here/coming, shipping bulk food halfway around the world is going to happen a lot less.]

    Unless some real magic surfaces in battery technology, to sustain N. American agriculture & population distribution in anything resembling their current forms, some biofuel usage seems necessary. I can certainly imagine having farm areas dotted with biomass converters that
    - use some of their input feedstock {miscanthus, switchgrass, woodchips, corn stover, (hemp? :-) , etc}input to drive the process, and produce ethanol/methanol. This at least recycles CO2, unlike fossil fuels.

    [www.rangefuels.com is an example of somebody trying to do that.]

    - or burn their input to produce electricity for grid baseload, and (hopefully, maybe) sequester CO2 [to actually draw down CO2].

    Anyway, it does no good to grow crops if you can’t get them to market … hence, biofuels. Fortunately, there is more land available than most people think. [See Energy Myth Three in book above.]

    Without some biofuels, one has to imagine 1)razing a lot of suburbs 2) splitting up big farms into ones small enough for individual families to work with lower mechanization, and 3)generally getting food growing closer to the consumers. Of course, 3) is a good idea anyway, but 1) and 2) wouldn’t happen easily. I’d guess that would need to raise the farm population back up to 10-20%, by reducing suburban/urban populations too far away from farms. Old Amish [horses; no electricity or tractors] would be fine. Others would have to learn farming anew, but at least with rural electrification it wouldn’t require going all the way back to 1900-style farming. It would still be a big shock, especially to current residents of New York City who must move elsewhere.

    Bottom line: agree on difficulty of hydrogen, but biofuels are really different, and at least so far, some biofuel really seems necessary. That doesn’t mean I love giant agribusinesses or every corn subsidy that comes along…

  4. #4 Dave Briggs
    December 12, 2007

    I have a post about a new way to produce hydrogen on my blog using a metallic alloy.
    I think we are going to see a lot of esoteric methods for production, and ways to overcome storage problems as outlined above, but there are working prototypes around and we will just have to wait over time to see which ones make it to the top via competition. The transition from the horse and buggy to the Model “T” took a while after all! LOL
    Dave Briggs :~)

  5. #5 Hydrogen
    November 26, 2009

    I had only heard briefly about microbial hydrogen generation. It sounds promising. I didn’t know it was developed at Penn State. Way to go Nittany Lions! At least in the meantime, cars can get an increased fuel efficiency by producing hydrogen and using it as a fuel additive. It might not do much, but at least it’s something.

  6. #6 Scan
    December 7, 2009

    Technologies need to have near-zero emissions of greenhouse gases and air pollutants over their entire life cycle, including construction, operation, and decommissioning. Industries will have to revamp if the world has any hope of slowing climate change from emissions. Most fossil-fuel heating, as well as ovens and stoves, can be replaced by electric systems and most fossil-fuel transportation can be replaced by battery and fuel-cell vehicles. Hydrogen, produced by using water, wind, and solar electricity by splitting water, called electrolysis, would power fuel cells and be burned by industries.

  7. #7 Harley Orion
    February 3, 2010

    I agree that we won’t see major adoption of hydrogen fuel without ample mechanisms to supply it. The microbial approach sounds really interesting. You might find this video interesting – it shows Air Force scientists splitting water using aluminum nanoparticles, yielding >1000 liters of hydrogen from one liter of water: http://bit.ly/butLK2